Photographic film is often used as a medium for recording a source image, and is constructed such that an image is recorded on one or more film layers that each contains photosensitive material, such as solar halide. Color photographic film is constructed using multiple film layers such that different image color information is recorded in different film layers according to the physical composition of each film layer. In general, one layer collects color information on each of the primary colors red, green and blue. Accordingly, these layers are referred to as the red, green and blue layers. Using these different layers effectively divides the source image according to its primary color components. However, each color layer also records some information from the other two color channels. For example, some red information becomes recorded on the green and blue film layers, some green information becomes recorded on the red and blue film layers, and some blue information becomes recorded on the red and green layers. This information associated with other channels will be referred to as crosstalk, or crosstalk information.
The field of electronic image processing electronically records, or digitizes, a representation of the source image. In conventional color scanning systems, separate red, green and blue sensing elements provide the red, green and blue information in separate information channels. These information channels are subsequently superimposed over each other in order to replicate the image. This process can degrade the resulting image if color separation between the red, green and blue information channels is not adequately maintained. In electronic film development, maintaining color separation between channels is inherently difficult, because of crosstalk, mentioned earlier.
Crosstalk, and particularly color channel crosstalk, can occur during the process of converting an image into a machine readable form. In conventional color scanning systems, the captured image information is typically tagged or otherwise conventionally identified according to its separable color and/or other image attributes, thereby facilitating separate information processing, computer display and printing.
As with electronic film development systems, conventional color scanning systems do not guarantee desired channel separation. Rather, a potential exists in such systems for variances in source medium characteristics such as film or document surface defects, light source or sensor tolerances, light reflection, refraction and absorption variations, and so on. Therefore, as with photographic film, using an image capture system can also result in channel crosstalk.
Noise can also be a problem in converting physical images to electronic representations. While crosstalk causes non-primary information to be included within a given channel, such non-primary information nevertheless is actual image information that is useful in accurately reconstructing the image. In contrast, noise is an image information anomaly, which will detrimentally affect the overall quality of a reproduced image.
Noise combined with crosstalk can be especially problematic, because noise tends tend to spread to all of the channels being operated upon. For example, noise in the red channel affects blue crosstalk information that exists in the red channel. When the blue crosstalk information from the red channel is recombined with the blue information from the blue channel, it brings some varying percentage of the noise from the red channel with it. This transferred noise tends to adversely affect the recombined information.
Accordingly, there remains a need in the art for an improved multiple-channel image processing.